The present invention relates to a stage for supporting, moving, and positioning articles, and more specifically, a stage for positioning an article in an electron beam or EUV-light lithography system used for manufacturing semiconductor devices.
Many devices such as reticles, semiconductor circuits and liquid crystal displays are fabricated using lithographic equipment, such as an electron beam lithography system. In the fabrication of circuits a article must be repeatedly and precisely positioned under the optics of the lithography system. Such precise positioning is necessary to ensure accurate alignment of the microscopic features being formed in a new layer with other microscopic features in the layers previously formed on the article during the fabrication process for semiconductor circuits.
Complex systems have been developed to precisely position an article, such as a wafer or reticle beneath the lithographic optics. A step and repeat system often uses an x-y positioning system to position the article on a positioning stage beneath the lithographic equipment, expose a portion of the article to a pattern of light or charged particles generated by the lithographic equipment, and reposition the article at another location to again expose the article to the pattern of light or charged particles. Many different types of positioning stages and linear motors which move the positioning stage into the desired position, such as beneath the lithographic equipment, nave been developed in an attempt to provide improved accuracy of article placement.
The articles being worked upon are typically supported and positioned using x-y guides with moving motors. Typically, such guides include separate x and y guide assemblies, with one guide assembly mounted on and movable with respect to the other guide assembly. Often a separate wafer stage is mounted on top of the guide assemblies. As the guides move during the positioning of the wafer, the magnet assemblies of the motors as well as other magnetic permeable materials also move. As a result, the shifting magnetic fields created by the magnet assemblies and other materials may interfere with an electron beam of an electron beam lithography system.
Electron beam lithography is used in the production of high quality patterns. The electron beam passes through magnetic or electrostatic lenses and deflectors capable of focusing the beam into the wafer plane and directing the beam in an x-y direction on the wafer. An election beam projection system typically includes an electron beam source, a deflecting system for deflecting the electron beam in a predetermined pattern, and magnetic projection lenses for focusing the electron beam. The deflected and focused beam is directed to an article which may be, for example, a semiconductor substrate or mask (reticle).
Conventional positioning stages do not typically shield the magnetic fields created by the moving motors or other moving magnetic permeable components from the electron beam lithography system. The magnetic fields may shift the electron beam and cause misalignment of the pattern on the article. Thus, it is desirable to provide a positioning stage which limits the movement of the magnetic fields during positioning of the stage while exposing the article to the electron beam. It is also desirable to shield the magnetic fields from the electron beam to accurately, reliably and timely move and position articles in an electron beam lithography system.
The present invention overcomes the deficiencies of the prior art by providing a stage positioning system which minimizes interference with an electron beam of an electron beam lithography system by magnetic fields created by the motors of the stage positioning system as well as other magnetic permeable components. The invention also provides a stage positioning system that can be used in an EUV light lithography system.
A stage positioning system of the present invention comprises a stationary frame, a slide movable relative to the frame in a first direction and a support platform connected to the slide and movable therewith in the first direction. The support platform is movably attached to the slide for movement in a second direction generally orthogonal to the first direction. The stage positioning system further includes first and second linear motors.
In the preferred embodiment, the first linear motor includes a first magnet assembly attached to the frame and a first coil device attached to the slide. As current is applied to the first coil device the slide will move in the first direction. The second linear motor includes a second magnet assembly attached to the slide and a second coil device attached to the support platform. As current is applied to the second coil device the support platform will move in the second direction.
The first magnet assembly may include a parallel pair of magnet tracks spaced apart a distance sufficient for receiving the slide therebetween. The first coil device includes coil members extending from opposite ends of the slide to interact with the magnet tracks. The frame may include a rail and the slide may include a slider block movably engagable with the rail. The slider block may contain bearings selected from rotating roller bearings, needle bearings, ball bearings, or gas bearings. The magnet tracks are preferably substantially shielded to prevent interference of the magnetic fields created by the magnetic assemblies with an electron beam.
The slide includes a pair of shafts extending generally parallel to a central longitudinal axis of the slide, and the support platform includes a pair of sleeves movably mounted on the shafts. The pair of sleeves may contain gas bearings to support the sleeves about the shafts.
The invention is also of a method of exposing an article in a lithography system, the method including providing a slide movably attached to a stationary frame such that the article can be positioned in a first direction, providing a support platform movably attached to the slide such that the article disposed on the support platform can be positioned in a second direction, providing a first linear motor to move the slide in the first direction and providing a second linear motor to move the support platform in a second direction, positioning the support platform by moving the slide to a selected position in the first direction, and exposing the article to light or an electron beam as the support platform is moved in the second direction. The procedure of moving the slide in the first direction followed by moving the support platform while exposing the article to light or an electron beam, is repeated until the selected exposure operation for the article is completed.
The positioning stage car be used in an electron beam lithography system, or an extreme ultraviolet (xe2x80x9cEUVxe2x80x9d) light lithography system. The lithography systems will comprise an electron beam source or an EUV light source, an optical projection system to project a pattern defined by a mask onto a surface of the article; a deflector system operable to position the electron beam on the article, and the stage positioning system of the invention. When an EUV light source is used, the deflector may not be necessary.
The stage positioning system of both the electron beam and the EUV light lithography systems preferably move the support platform in the first direction while the article is not being exposed to the electron beam or EUV light. The support platform is then moved in the second direction while the article is being exposed to the electron beam or EUV light. This allows the magnet assemblies that move the support platform in the second direction to remain stationary during the exposure of the article. It should be noted that electron beams are sensitive to magnetic fields whereas EUV light sources are not.
The invention will be better understood by reference to the Detailed Description of the Invention when taken together with the attached drawings, wherein:
FIG. 1 is a perspective of the stage positioning system of the present invention;
FIG. 2 is a perspective of the positioning system of FIG. 1 with parts removed and broken away to show detail;
FIG. 3 is a cross-sectional view taken through and including line 3xe2x80x943 of FIG. 2;
FIG. 4 is a perspective of a slide of the positioning system of FIG. 1;
FIG. 5 is a perspective of the slide and a portion of an x linear motor of the positioning system of FIG. 1 with a support platform removed to show further detail;
FIG. 6 is a perspective of a support platform assembly of the positioning system of FIG. 1;
FIG. 7 is a perspective of a portion of an electron beam projection system with parts broken away to show detail; and
FIG. 8 is a representation of an EUV light lithography system using the positioning system of the invention.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.